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The concepts involved with the experimental techniques of Electric Field Induced Second Harmonic generation (EFISH), dipole moment measurement, and solvatochromism, are introduced with particular application to the properties of organic molecules. A number of organic chromophores are introduced, but emphasis is applied to the study of tetracyanoquinodimethane (TCNQ) derivatives which are expected to possess large dipole moments (µ) and large hyperpolarisabilities (β). Furthermore, the behaviour of and with respect to the local environment of the molecule is discussed where a novel evolution is predicted from theoretical calculations. The measurement of µ, is discussed with particular reference to the geometry of the local field factor and the size of the molecule. Consequently, the choice of local field is found to be critical when dipole moments are large, as is the case with the TCNQ derivatives. The EFISH experimental technique is introduced where the calibration of the experiment is discussed. The measurement of the molecular figure of merit, µβ at 1.064 µm and 1.907 µm in chloroform and dichloromethane is presented for the TCNQ derivatives, again paying attention to the geometry of the local field factor. µβ is found to be moderate for most of the compounds, but β is found to be unexpectedly small. This is partly due to the fact that µ is large. A novel evolution of the transition frequency with solvent polarity is found for three of the chromophores under study, where the solvatochromic shift reverses. Solvatochromism experiments are conducted with binary solvent mixtures to ascertain the position of the cyanine limit (β=0) with respect to reaction field. It is found that the materials reside close to the cyanine limit in chloroform and dichloromethane. This is attributed as a reason for the low β measurements. Comparisons of µ and β are also made with Sum-Over-State calculations. A better correlation is found for ellipsoidal local field factors.

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Thesis (M.S.)--Missouri University of Science and Technology, 2010. / Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed Dec. 23, 2009). Includes bibliographical references (p. 60).

Thesis (Ph. D.)--University of Texas at El Paso, 2009. / Title from title screen. Vita. CD-ROM. Includes bibliographical references. Also available online.

The muon is a useful probe of magnetic fields in superconductors, but knowing the field seen by the muon is often of limited value until we know where the muon is in the crystal lattice. In this thesis I employ two independent theoretical methods to search for candidate muon sites: the potential energy field method, which seeks the minimum of the electrostatic potential of the μ⁺, and the magnetic dipolar field method, which compares the calculated magnetic field (due to the host electronic, atomic or nuclear dipolar fields) with the observed local fields at the muon. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

The term “soft matter” applies to a variety of physical systems, such as liquids, colloids, polymers, foams, gels, and granular materials. The most fascinating aspect of soft matter lies in the fact that they are not atomic or molecular in nature. They are instead macromolecular aggregates, whose spatial extent lies in the domain 1 nm to 1 ¹m. Some of the most important examples of soft matter are polymers, which exhibit intriguing and useful physical properties. In this work, the adsorption and self assembly of linear and star polymers on smooth surfaces are studied using coarse-grained, bead-springmolecular models and Langevin dynamics computer simulations. The aim is to gain insight on atomic-forcemicroscopy images of polymer films on mica surfaces, adsorbed from dilute solution following a good solvent-to-bad solvent quenching procedure. In the case of linear polymers, under certain experimental conditions, a bimodal cluster distribution is observed. It is demonstrated that this type of distribution can be reproduced in the simulations, and rationalized on the basis of the polymer structures prior to the quench. In addition to providing insight on experimental observations, the simulation results support a number of predicted scaling laws such as the decay of the monomer density as a function of distance from the surface, and the scaling of the filmheight with the strength of the polymer-surface interactions. Star polymers represent a special class of polymers, in which one end of each linear chain is tethered to a small central core to forma single particle. The discovery of these molecules led to the synthesis of a wide range of new materials. Their structures are effectively considered as intermediate between those of colloids and linear polymers. We explore the behaviour of the star polymers (which are like “soft colloids”) in the proximity of a surface, using Langevin dynamics simulations. A number of different measurements such as the height, radius of gyration, and asphericity of adsorbed stars with different number of arms, are shown to provide valuable insights on experimental findings. The simplest soft matter systems consist of spherical, rigid colloidal particles. Examples of such particles are chemically synthesized polystyrene or silica particles. We investigated the neighbour distribution in a two-dimensional polydisperse harddisk fluid, corresponding physically to a colloidal monolayer. The disk diameter distribution was defined by a power-law with the aim of realizing a scale-free nearneighbour network. Scale-free (power-law) behaviour is found in many important networks, for example, in transportation systems, biochemical reactions, scientific and movie-actor collaborations, and sexual contacts. We have provided the first example of a scale-free network in amodel condensed-matter system. Finally, we use genetic algorithms, a method for efficiently searching for minima on energy landscapes, to investigate the ordered equilibrium structures formed by binary mixtures of anisotropic dipolar particles confined on a plane, under the presence of an external magnetic field. The anisotropy of the interparticle forces is controlled by tilting the external magnetic field with respect to the plane. Initially, as the field is tilted the structures are only slightly perturbed, but once the anisotropy exceeds a critical value, completely new structures emerge.

The dissertation first investigates gravity wave generation and propagation from jets within idealized vortex dipoles using a nonhydrostatic mesoscale model. Several initially balanced and localized jets induced by vortex dipoles are examined here. Within these dipoles, inertia-gravity waves with intrinsic frequencies 1-2 times the Coriolis parameter are simulated in the jet exit region. The ray tracing analysis reveals strong variation of wave characteristics along ray paths. The dependence of wave amplitude on the Rossby number is examined through experiments in which the two vortices are initially separated by a large distance but subsequently approach each other and form a vortex dipole with an associated amplifying localized jet. The amplitude of stationary gravity waves in the simulations with a 90-km grid spacing increases nearly linearly with the square of the Rossby number but significantly more rapidly when smaller grid spacing is used. To further address the source mechanism of the gravity waves within the vortex dipole, a linear numerical framework is developed based on the framework proposed by Plougonven and Zhang (2007). Using the nonlinearly balanced fields as the basic state and driven by three types of large scale forcing, the vorticity, divergence and thermodynamic forcing, this linear model is utilized to obtain linear wave responses. The wave packets in the linear responses compare reasonably well with the MM5 simulated gravity waves. It is suggested that the vorticity forcing is the leading contribution to both gravity waves in the jet exit region and the ascent/descent feature in the jet core. This linear model is also adopted to study inertia-gravity waves in the vicinity of a baroclinic jet during the life cycle of an idealized baroclinic wave. It is found that the thermodynamic forcing and the vorticity forcing are equally important to the gravity waves in the low stratosphere, but the divergence forcing is again playing a lesser role. Two groups of wave packets are present in the linear responses; their sources appear to locate either near the surface front or near the middle/upper tropospheric jet.

Thesis (Ph. D.)--Auburn University, 2008. / Abstract. Includes bibliographical references (p. 121-127).

Thesis (Ph. D.)--University of Washington, 2001. / Vita. Includes bibliographical references (p. 84-94).